article: Robots are supposed to run on batteries, right? Well not all of them.
  Scientists in England have built a kind of small robots that get their energy from dead flies, bad apples, or sugar.
  One robot, called Slugbot, was even designed to hunt  garden slugs for dinner!
  What's up with all that food?
  Well, scientists at the Bristol Robotics Laboratory want to invent robots that can operate for a long time in dark, dirty, or dangerous places.
  Many of those spots, like the seafloor or Antarctica, don't have electrical sockets .
  So inventor Chris Melhuish came up with a better idea: Build robots that get their energy just like animals do by hunting and eating food from their environment.
  One robot, called Ecobot II, could run for 12 days on a diet of eight flies! Of course, it'd still get a lot more power from one AA battery, though.
  Melhuish says his team is now working on a new and improved robot, called Ecobot III, which will have a better digestion system.
  It seems that after an eight fly dinner, Ecobot II couldn't deal with the leftover  "waste".
  Maybe restrooms in the future will have signs for boys, girls, and robots.
question: From the passage, we can infer that a slug .
options: is a kind of insect is a kind of fish can't see Slugbot can eat Slugbot